Upstream uses >= here. It was changed in GPDB, to use > instead of >=. but
I don't see how that's more correct or better. I tracked that change in
the old pre-open-sourcing repository to this commit:

commit f3e98a1ef5fc5915662077b137c563371ea1c0a4
Date: Mon Apr 6 15:04:33 2009 -0800

   Fixed guc check for ReservedBackends.

   [git-p4: depot-paths = "//cdb2/main/": change = 33269]

So, there was no explanation there either, what the alleged problem was.